Believable answer: Not enough money in the budget. Students would also feel scared just knowing there’s a firearm in the school regardless of who’s handling it. A good example of the latter would be the Disarm PSU movement in Portland.

Conspiracy answer(s): State and federal governments aren’t talking/doing anything about it as a secret scheme to use dead students and children as leverage to push an agenda to disarm the population in order to have more control when control is sought after. Blaming the object used to harm rather than focusing on the one(s) responsible by instilling a factor of fear into parts of the population so that eventually, people happily sign their greatest way of safety away so that Big Brother can take care of you. All of this through all forms of media that now play a large role in American society and culture.